Hey! - I gave you credit for the idea in post #366!!! The new dual aluminum plenums are at the fabricators being made, and I have removed the side scoop to open it up to blow cold air on the two K&N filters. You can see the working drawings below in the previous post. Interesting thing - Airboxes and cool air induction are more than just cleaning air getting to the carbs. I learned that Airboxes also can be optimized for carb cooling and ease of maintenence. I'm trying to get this where cool air not used by the carbs flows between the carbs and helps keep then cooler as well. I addition, the way I am copying the Jalpa set up allows quick and easy sevicing of the area between the carbs without having to remove the air horns. I've also learned that some of these cool air induction systems are not inclement weather friendly, so have to make sure that a sudden deluge will not water soak the filters. Pictures in a couple of weeks. DJ, I do think your Air fuel looks pretty good; If you keep it around 13, you can't go too wrong. Your accel pump firing behavior on the graph is better than mine. You'll see all the benefit above 6000 rpm once you sort your ignition out. Also remember, that even though corrected for temperature, the reality is the weather when you do the test will affect the numbers. That all said, your jetting is right on I think. Would suggest going up one level hotter plug. Looks great! best rt 2 weeks from retirement!!!!! Image Unavailable, Please Login
And I thank you for it!!! It just seems that my post was completly ignored..and that is why I have stayed out of this thread for a long while. The flat plane crank design needs 2 seperate airboxes for each bank to work the best..basicly its 2 four cylinder engines attached at the crank!!
I was also looking at the smallish plenum volumes and set up on newer Ferraris, then it hit me: Just as we optimize air velocity in the carbs there is an air velocity and air column inertia in the induction system and the plenum acts as an extension of the total tract length. So, much like setting up carbs and velocity stacks, I am now learning about balance between a low restriction system (short airpath) and providing some air velocity/inertia (longer length) in the induction system to feed the even induction pressure waves on each cylinder bank. The previous rule of thumb I had read was that airbox volume should be about 1.5 the engine displacement. While that is anout right for the 308 airboxes, the newer models seem to eschew this. I think the 360 system really shows this well, and is a study model for me for a flat crank induction We'll see.
It was a cold day Saturday, about 45 degrees max and probably 60% humidity (or more). I can't recall the exact plug that I am using but it is hotter than stock. The tech at the dyno suggested that I may be running too large a gap resulting in a missfire due to the high cylinder pressure above 6,000. She pulls very smooth all the way through. A joy to drive. DJ Dyno day here, http://www.ferrarichat.com/forum/showthread.php?t=98116 A real blast with an F40, 550, 430 and later a C5R, 911 TT and Viper. I even ran my 240Z
Here are the roughed out dual plenum intakes; The snouts will be refined but I must say the aluminum welding on the box is aircraft quality. I've also removed the side vent and am working on an appropriate duct. Note the space now between the carbs for cooling air flow. I was going to paint them black or red, but I may just leave them aluminum... I have no idea if this will affect the sound. Image Unavailable, Please Login Image Unavailable, Please Login
Very cool Russ. Aluminum would look best. Those things are begging for inlets on the drivers side as well.
I modified the aircleaner on my first 77 308 quite a while back, after this thread started. But the car was (and still is) in peices and I never was able to see what difference it would make. That car has/had P6 cams and 9.6 pistons, and i though it howled pretty good then. I always was wondering how the modified aircleaner would perform. I bought this second 308 (21645) back in April initially as a parts car to put 21181 together and get her back on the road, but this darn thing ran and was in pretty good shape, so I decided to make it a driver. Finally, after working on it the last couple months got it out the other day and am running the modified aircleaner. HOLY COW does that sucker make noise. Its easily a lot louder than that P6 motor with the muffled aircleaner. It sounds freakin awesome. I have to go get this oil leak fixed and get out and tear up the roads some more.
I'm a huge fan of the Russ airbox mod. As far as I'm concerned, it's the second thing you do to a carbed 308....right after replacing the fuseblocks! ;-) Birdman
great mod, but forcing cold air into the intakes is the way to go. i had individual air cleaners on my 308, once the car warmed up, it ran like crap sucking in all the hot engine air. since i did the drivers side mod to my 308, my car sounds terrific from the drivers side, and i constantly get cold air into the engine, and it always runs strong - colder air is denser air. sorry about the hijack. john Image Unavailable, Please Login Image Unavailable, Please Login
I do agree that getting air to both sides the single plenum stock airbox is helpful and I am sure your extra feed ducts improved the air availability. Glad to hear of a good result. The way it's set up, even with unequal flow to each side, the common plenum inside the air filter should help equalize flows to all of the intakes. To hijack my own thread - what kind of yellow fuel hose is that?
Also, have replaced the stock air horns with the low rise high flow that Kermit used to sell. I think this will buy me more volume over the bellmouth and flow. Will test this out this weekend. Image Unavailable, Please Login
Hi Russ sorry to hijack our own thread with my mod. I am impressed with your air cleaner setup, very clean. Keep us posted on the performance. It is hard to be creative with air induction, i live at 7200 feet above sea level, so any help i can get with cooler denser air is welll accepted. the yellow film on the fuel line is called MLI, from Lockheed. Used as spacecraft insulation. it is actually layered film with an insulator sandwich, i used it to keep my fuel lines cool. Just trying to keep fuel and air cool under the hood. Any insulating material i am sure is sufficient, it just needs to be thin to clear all the linkages.
wet for a short run this evening after ambient temps came DOWN into the 90s. Subjectively it seems to run smoother than with the stock, certainly sound wise., and compared to all of the previous permutations, this one seems to have loosened up the personality a bit - very attitudinal. WTF does that mean? - well, the K-Jetronic injected Mondial is a very sophisticated smooth running machine at all rpms, although with a little muted throttle response. Since going to carbs, the experience is much edgier, with the Webers giving a 'right now' BAM! response. Of course I now have about 290 hp at crank with about 243+ ft-lbs of torque since converting to the Webers, so that also makes a difference. That combined with the sound of the Webers it is really quite raw and visceral compared to the injected model. I would imagine it is akin to the way people compare carburreted versus K-Jetronic Boxers. Although a wee bit louder than the stock box, this is the most aggressive and engaging combination yet.
after read reading ( most ) of the 21 pages, i did my airbox. have not driven car yet. going to order 135s and 190s for the carbs..... will see tomorrow ! Image Unavailable, Please Login Image Unavailable, Please Login
Michael, Did you just give your ***** a big hair cut or is all of that furr out of the air cleaner?? baffled-but still curious - hope it wasn't the kitty. chris
its from the airbox. my K&N full size filter comes in today. the old ferrari air filer with the brown element is flexable, and you can get it out of the airbox with it installed. the $80.00 piece of crap UFI filter i purchased from on eof the " ferrari parts suppliers " is too rigid to fit in the box easily. my guess is that you have to have the airbox out and the airhorns off. then reinstall everything after the airfilter is put in place. the blue plastic from the new UFI filter started peeling loose. i dont want that crap getting sucked into a carb. i am sticking with Baldwin and K&N for now on. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
I am still marveling at this whole deal. I have been studying the 308 off and on since it was made. Back in the late '90's I joined the Flist, and gained a great deal more knowledge about these cars, but until this thread started I do not believe it was generally known by anyone how restrictive the aircleaner really was. I am sure someone seen it along the way, but it just wasnt public knowledge. When this started and I seen the first pictures, it blew me away so much I almost ran to go look at MY airbox. Hmmm, mines plugged up too. Well, not anymore it wasnt. Little did I know it would be over a year before I would get to "hear" it. My first 308 had high compression with P6 cams, and made a lot of carb noise with the aircleaner off, a lot more than this second car with stock cams and pistons does. But I never heard the P6 car with this mod, only this second car. But my Lord the sound it makes is phenomenal. In fact its so loud I can see why they muffled it. I do not object to the noise, its not THAT loud, but I can see it being objectionable to the posuer crowd. But just how much better does it breath? This second car came with a KN airfilter, and I see no reason to run anything different. Its a high performance car, it should use a high performance filter. I have had the aircleaner off the car about 4 times now, so each time I am handling the element and looking at it. What is odd is that before, the aircleaner was always clean, never seen anything in it. Now everytime I open this thing I find dirt and bits of crap. Yesterday I found a birds feather in it. But the interesting thing is that most of the debris is on the far left side of the airbox, so there must be a lot more airflow back there. One other thing of note. I remember way back as a kid being around an older man working on a hotted up V8 with dual 4bbl's. The sounds it made were interesting, but one thing he brought my attention to was that as you opened the throttles, in that moment of time before the motor wound up to high, he claimed if you listened you could hear the intake valves snapping shut. So many cars over the years have become so muffled you dont hear any real induction sound anymore. And even if you could, the opening of the plenum and manifolding is a long ways out from the valves. The only times I have ever heard that noise were on cars with big carbs when they opened up at low rpm. And thats been so long ago I totally forgot about it. But the other day out plying with the 308, I heard that noise again, and drove around at low speed stepping on the throttle, just smiling and having fun. I dunno if its really the sound of the valves, but its a neat sound. And you would NEVER hear it with all that stuffing crap in that airbox. Between that valve noise and the gurgle, hiss and honk the carbs make, in symphony with the whine of the gearbox and the purr of the exhaust, its just lovely. Simply lovely. Maybe now those intake screens the Germans made the cars have wouldnt be such a bad idea. You could suck in a bird with it now.
You can't install the cover and trumpets with the air cleaner in place. The air cleaner gets in the way of installing the nuts to hold down the trumpets.
looking at the pic carreaper posted, it has occured to me that the 'wool' or absbestos packing might be there to reduce the chance of a fire from a backfire. thoughts?
Backfire would come through the carbs into the air box. What is the wool/insulation going to do to stop that? It's on the air inlet side.
as tvine pointed out, not stop a backfire but supress an ingnition of the fuel vapors in the engine bay from a backfire. i could be offbase but it does make you wonder.
HEY GUYS, i caught that crap on fire TWICE with the dremmel tool while cutting the welds and the preforated metal. it was NOT easy to put out either. ( threw sand on it) i do not think its fire retardant, i think it may be another cause to so many 308s burning up.
